Valveless pulsejet smoke generator



Jan. 16, 1962 M. A. PERSECHINO 3,017,367

VALVELESS PULSEJET SMOKE GENERATOR 2 Sheets-Sheet 1 Filed Oct. 22, 1959 INVENTOR MAR IO A. PERSECH l NO ATTORNEY Jan. 16, 1962 M. A. PERSECHINO 3,017,367

VALVELESS PULSEJET SMOKE GENERATOR Filed Oct. 22, 1959 2 Sheets-Sheet 2 ENTOR MARIO A. PERSECHINO ATTORNEY United States Patent VALVELESS PULSEJET SMOKE GENERATOR Mario A. Persechino, Chesapeake Beach, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed Oct. 22, 1959, Ser. No. 848,168 8 Claims. (Cl. 252-359) (Granted under Title 35, U.S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates in general to fog producing machines and, more particularly, to a pulse combustor of the valveless type used for producing dispersions of liquids in air or other gases for the production of fogs.

Machines such as those comprising this invention are sometimes called fog machines and are used for the production of fine particle dispersions of liquids in air to produce fogs, such as fogs of oil particles, as in the production of military smoke screens or fogs of insecticidal or the like liquids which are used for the control of insect pests, fungi, molds, etc. The essential elements of a mechanical fog generator are a source of heat and a means for vaporizing oil and ejecting the vapor into the atmosphere. Upon contact with ambient air the oil vapor is condensed into a white fog composed of minute liquid particles. The heat is ordinarily supplied by a small burner, using gasoline or diesel oil, with a small blower furnishing air for combustion and larger blowers for imparting a high velocity to the oil particles. Such devices are heavy and expensive machine installations having numerous rotating parts and the dispersions produced by such prior machines are even then frequently of unsuitably large or widely varied particle size. Furthermore, the production of dispersions of liquids in air or other gases by such prior machines has required highpressure steam or rotating equipment, or both, of complicated and expensive character, needful of frequent servicing and attention. Prior machines utilizing steam in conjunction with the fog fluid have been prone to rapid coking of the boiler tubes, requiring frequent replacement thereof, and prior machines not utilizing steam have sulfered from both rapid coking of the fog fluid nozzles and associated parts and flash-back and torching at the fog exit nozzle. Heretofore, gas turbine engines as a prime mover and valve pulse jets have been utilized to produce fogs by injecting oil directly into the hot exhaust. These devices are expensive, have movable parts, and will not produce fogs uniformly for long periods of time.

The valveless pulsejet fog generator of the present invention overcomes the drawbacks of the above-mentioned fog machines and provides a lightweight portable device suitable for accomplishing fog generation without the use of any movable parts in the generating device. The valveless pulsejet fog generator of the present invention is capable of vaporizing a variety of fogging oils and otters the following possible advantages over existing units:

(1) Low manufacturing costs.

(2) Little or no carbon deposit in the vaporizing chamber. 7

(3) Operation with no moving parts, thus promoting long service life with little or no maintenance.

(4) The ability to operate on a variety of fuels, including the more viscous fuel oils and the provision of a device made with the utmost simplicity.

The present invention is useful in many military operations such as camouflaging large areas against aerial detection bombardment; camouflaging river crossings, erec- 3,017,367 Patented Jan. 16, 1962 tion of bridges or gun implacements; camoufiaging naval transportation in unloading areas against attack and observation; camouflaging amphibious landing operations against both shore and aerial bombardment; obscuring military targets from infrared photography and seeing devices; and dissemination of aerosols containing toxic materials for use in controlling diseases such as malaria, etc.

The valveless pulsejet fog generation device of the present invention canbe mare as a portable generator for use of small boats, auxiliary vessels, and for use ashore, whereas larger units are required for permanent installation aboard large combat vessels, etc. The valveless pulsejet device is also adapted for use with either gasoline or diesel fuel oil such that the valveless pulsejet can be adapted for either shore base or shipboard operation and make use of the available fuels.

The fog generator of the present invention will produce good quality fog coverage in very short periods of time and is capable of maintaining good quality fog coverage for long periods of time for continuous operation. The generator is also capable of using standard fog-oil both winter and summer grades as well as other oils available aboard ship or ashore. The generator is capable of being started at low temperatures of about minus 65 F. and is capable of producing a fog without serious decomposition of the fog-oil and will produce a particle size optimum for screening purposes. The optimum size has been determined as being 0.6 to 0.7 micron diameter.

It is therefore an object of the present invention to provide a smoke or fog generator which requires little or no maintenance to the burner and vaporizer assembly.

Another object is to provide an improved fog machine of light weight, of readily portable character, capable of being readily carried by hand or by light field equipment, and also capable of being carried by airplanes, helicopters or small ships, as well as large ships.

Still another object is to provide a device which operates with little or no carbon deposition in the vaporizing chamber, simplicity of design, and can be made with low manufacturing cost.

Yet another object is to provide a fog generator adapted to operate on a variety of fuels and fogging oils in very low temperatures as well as in high temperatures.

Still another object is to provide a light weight device capable of giving long service without faulty operation.

Other and more specific objects of the invention will become apparent upon a careful consideration of the following detailed description taken together with the accompanying drawings in which:

FIG. 1 is a sectional view along the axis of a preferred embodiment of the invention;

FIG. 2 is a front cross-sectional view illustrating the fuel inlet and fog oil inlets of the device;

FIG. 3 is an enlarged section of the fuel and fog oil inlet as well as the ignition spark plug;

FIG. 4 is a plan view illustrating a working model in accordance to the present invention; and

FIG. 5 and FIG. 6 are modifications of the device shown in FIG. 1.

The fog generator as shown for illustrative purposes comprises a valveless pulsejet 10 surrounded by a stainless steel sleeve 11 closed at the forward end of the pulsejet and opened at the opposite end the same as the pulsejet. As illustrated, the pulsejet is classified as a 3% inch pulsejet having a 5-inch sleeve surrounding the pulsejet. The pulsejet is mounted within the sleeve by welding (or any other suitable means) the fuel-air inlet tube 12 of the pulsejet to the sleeve such that the pulsejet and the sleeve are coaxial. The exhaust end of the pulsejet is secured for a sliding fit in brackets 13 rigidly secured to the inner surface of the sleeve. The spacing between the 3 pulsejet engine and the sleeve forms a fog oil vaporizing chamber and the sliding fit at the exhaust end of the pulsejet permits movement of the pulsejet within the sleeve due to expansion and contraction during the use thereof.

The valveless pulsejet combustor is in the general form of a cylindrical tube closed at the forward end and open at the rear end, the forward portion being of relatively large diameter and short length to form a combustion chamber 14 having its exhaust section 15 connected to a reducing portion 16 with the rearward portion or exhaust portion of smaller diameter and greater length to form a tail section. The end 17 of the tail section is open and flared outwardly tohave the same diameter as the combustion chamber. The open end of the sleeve extends beyond the end of the valveless pulsejet and provides a suitable fog-oil exhaust gas mixture in section 18, and also provides sufficient length to prevent oxidation of the fog oil by oxygen inlet from the outer open end of the sleeve. A fuel and air inlet or combustor inlet tube 12 is provided at the combustion chamber wherein the end of the fuelair tube Within the combustion chamber can be made in accordance to the tube end described and shown in Paten't No. 2,795,105; however, any satisfactory tube ending can be used to carry out the teaching of the present invention. For the purpose of admitting fuel into the combustion chamber two oppositely disposed fuel ports 19 are provided on the upper side of the fuel-air inlet tube and near the combustion chamber. Any suitable fuel injection nozzles can be used for the purpose of admitting fuel to the combustion chamber. For initial ignition of a fuel-air mixture in the combustion chamber, suitable ignition means is provided in the form of a spark plug 21 which is mounted on the top of the fuel-air injection tube and forward of the fuel inlet nozzles. The spark plug 21 may be energized and controlled through any known or other suitable means not shown for the purposes of simplification of the drawing. The fuel injector has spray orifices extending therethrough directed toward the combustion chamber. Thus the fuel injector is permitted to spray fluid fuel into the inlet tube wherein the fuel mixes with fresh air flowing in the combustor inlet tube toward the combustion chamber to form a combustible mixture. A fuel supply line 22 is connected to the fuel injector to supply a fluid fuel under pressure from any suitable system such as shown in FIG. 3.

For illustrative purposes only, afog generator in accordance with the present invention making use of a 3.5 inch valveless pulsejet engine can be made according to the dimensions shown in FIG. 1 for satisfactory operation in producing satisfactory fogs.

-It may be pointed out that in a valveless pulsejet enginE the combustion zone and exhaust tube portions shown may not be discrete and entirely separate elements for in many pulsejet engines the two portions, that is the combustion zone and the exhaust tube, blend together both in construction and function. In the valveless pulsejet operation it is difficult to establish that portion of the apparatus wherein combustion ceases and the exhaust tube portion begins. However, in valveless pulsejet engines of this character there is a combustion zone portion in which combustion predominately occurs and an exhaust tube portion from which the products of combustion are expelled in a series of pulses, hence the name valveless pulsejet engine. As shown, the combustion zone is of larger diameter or cross section than the exhaust tube portion of the engine; however, it is possible to make some engines in which the combustion zone is equal to or even smaller in cross-section as compared to the exhaust tube. Also pulsejet engines can be made of larger or smaller diameter than the illustrated engine; therefore, it is to be understood that FIG. 1 is merely illustrative of a valveless pulsejet engine which may be utilized as a component part of the present invention without limitation of the scope thereof.

FIG. 2 is a cross-section through the combustion zone section illustrating more clearly the relationship of the fuel nozzle ports 19 and the fog-oil nozzle ports 23. As shown, the fuel nozzle ports are positioned at such an angle that the fuel injected through a fuel nozzle in each port would be directed toward the axis of the combustor inlet tube such that the fuel can be properly mixed with the air entering through the air inlet tube. The fog-oil ports 23 are positioned outwardly of the fuel inlet nozzles and to the rear thereof such that the fog-oil ports will direct the oil into the area between the sleeve and the pulse jet combustion chamber and to the rear thereof along the exhaust. An additional fog-oil port 24 is provided along the axis at the closed end of the sleeve such that oil entering into the port will be directed over the full length of the combustion chamber. FIG. 2 further shows the position of the spark plug and the relationship of the spark plug to the fuel injection ports.

FIG. 3 illustrates the fuel and fog-oil inlets in an enlarged side view.

FIG. 4 illustrates a fog generating device set up for permanent construction having a fuel tank 31 in which the fuel line 22 from the tank to the fuel inlet nozzles includes a pump 32 and a control valve 33. The fog-oil is directed from a tank 34 to a line 35 which includes therein a control valve 36. As shown, the fog-oil tank is pressurized by any convenient means 37 for the purpose of forcing the oil from the tank into the feed line. The section of the device in which the fog-oil mixes with the exhaust gases includes a thermocouple 38 for the purposes of indicating the temperature of the mixture. Under certain conditions, the temperature of the mixture controls the size of the fog-oil droplets which enter the atmosphere. The sleeve has attached thereto mounting brackets 39 for the purpose of securing the fog generating device to any structure desired.

In operation of the device a gaseous fuel such as butane, propane or the like, gasoline or diesel fuel may be used. In the use of gaseous fuel such as butane, propane or the like, starting may be accomplished without injection of auxiliary air or use of auxiliary heating means for the combustion chamber. However, where liquid fuel is used, that is fuels not self-gasifying such as gasoline, starting may be accomplished by the injection of auxiliary air through the air inlet tube at sufl'icient pressure and volume to break up the fuel entering through the fuel nozzles and provide a suitable starting mixture, air can be supplied from any suitable source and is not shown for simplification of the drawing. In the event diesel fuel is used, a preheating period is required before the engine will operate. 'Preheating is accomplished simply by placing a small compressed air nozzle in the intake tube and partially opening the fuel regulating valve, allowing a small amount of fuel and air to burn continuously in the combustion chamber until sufficient heat is released to vaporize the diesel oil. As soon as the diesel oil is vaporized sufliciently and resonance occurs, the fuel valve is fully opened and the air supply and ignition are turned off. Both air pumping and ignition are maintained automatically by means of the resonant intermittent combustion cycle at approximately cycles per second and will be explained more fully hereafter. In the use of gasoline or diesel fuel, the use of the ignition system and the auxiliary air through the air intake tube is used only until the combustion starts and then the auxiliary air and ignition system is turned off. After starting, and allowing a few seconds of preheating, the fog-oil is fed into the vaporizing chamber surrounding the pulse jet engine, and is force fed continuously into the vaporizing chamber at low pressure approximately 5 to 15 pounds per square inch-for continuous operation. As the fog oil flows over the combustion chamber and exhaust pipe of the valveless pulsejet, the fog oil vaporizes and is pulled into the fog-oil, pulsejet exhaust mixing chamber by the exhaust gases from the pulsejet. The vaporized fog-oil and exhaust gases are expanded into the atmosphere where the vaporized fog-oil condenses into fog. To improve the uniformity of vaporization, the fog-oil can be preheated by wrapping the feed tube about the sleeve prior to introduction into the fog oil chamber as shown in FIG. 6.

The continuous operation of the valveless pulse jet engine without the aid of any outside means for ignition is as follows: described above; after self-ignition of the mixture of fresh air and fuel, the ensuing explosion causes a sudden pressure rise which starts a gaseous flow out of the inlet tube and exhaust tail pipe. Initial forces maintain the outflow until the pressure in the combustion chamber falls below atmospheric pressure. At this time fresh air and fuel are drawn into the combustion chamber through the air intake tube Where the fuel and air mixture is fed into the combustion chamber. During intake of the air and fuel, a mixture of exhaust gas and oil vapor combined in the mixing chamber at the end of the tail pipe of the valveless pulsejet engine are ejected at high velocity at the generator exit where it is mixed with ambient air to form fog. As the exhaust gas and oil vapor emerge from the end of the generator, the pressure at the exhaust exit end falls below atmospheric and air and condensed vapor are drawn back into the mixing chamber and, at the same instant, oil vapor mixed with exhaust gas is drawn into the tail cone of the pulsejet and residual, overexpanded exhaust gas is driven up the tail pipe effecting a slight pressure rise in the combustion chamber. The back flow of the mixture of the exhaust gases, air and oil vapor into the exhaust tail pipe of the engine compresses the fuel-air mixture in the combustion chamber. The fresh charge in the combustion chamber begins to burn and the heat release is completed exposively as the previous cycle and the resonant cycle is repeated for continued operation of the pulsejet combustion. Both air-fuel mixture pumping and ignition are carried out automatically by means for the resonant, intermittent combustion cycle of about 100 cycles per second.

During the ejection of the combustion gases through the exhaust tube of the valveles pulsejet engine, the gases draw with it the vapor gases of the fog-coil produced circumferentially about the valveless pulsejet engine by the heat from the pulsejet engine. The mixture of the exhaust gases and the oil vapor from the fog-oil are ejected at high velocity in the form of billowing white clouds of fog. It is to be noted that while the pulsejet engine is operating the fog-oil which flows over the combustion chamber and exhaust pipe of the valveless jet engine vaporizes and enters the mixing chamber at the end of the exhaust end of the pulsejet as vapors wherein the vapors mix with the exhaust of the pulsejet. The straightthrough design and the pulseatory nature of the flow tend to keep the unit free from carbon accumulation. Furthermore, the fog-oil is vaporized in a dead end space where there is no concentration of oxygen to cause oxidation. The fog-oil vapor sucked out of this space by the high velocity exhaust jet is mixed with very hot gases, but this gas has very low oxygen content as excess air is not required for pulsejet combustion. When the exhaust and oil vapor mixes with the ambient air it does come in contact with an atmospheric concentration of oxygen, however the mixture is chilled so rapidly that any flame is extinguished and little oxidation occurs. It has been determined that very little thermal cracking, evidenced by the lack of carbon residue on the tube surfaces, takes place with this design as a very small percentage of the oil comes in contact with the high exhaust temperature for a small interval of time. After intermixture of exhaust gas and fog-oil vapor, most of the oil is subjected to temperatures slightly above the final mix temperature of 900 F. On emerging from the mixing chamber and upon contact wtih ambient air the oil vapor is condensed into a white fog composed of minute liquid particles. The size of these particles depends upon the fuel used,

The operation of the engine is started as the exhaust temperatures, the pressures involved and the amount of fog-oil and fuel used. It has been determined that the most useful fogs are made by particle sizes of about 0.6 to 0.7 micron diameter.

FIG. 6 illustrates an embodiment of the invention wherein the fog-oil is preheated prior to injection into the fog oil chamber between the pulsejet engine and the surrounding sleeve. As shown the supply line 45 is first coiled about the surface of the sleeve opposite to the rear part of the pulsejet engine combustion chamber and a portion of the exhaust tube. The supply line is then coiled about itself in the vicinity of the air inlet tube. In this modification the fog oil is preheated by the heat from the surface of the sleeve and then further heated by the exhaust gases which are blown out of the inlet tube during combustion of the fuel in the combustion chamber of the pulsejet and normal operation thereof. The heat transferred to the fog oil from these heat sources decreases the temperature difference between the fog oil at the injection ports and the vaporizing chamber. Utilizing the heat available from the intake tube increases the vaporizing capacity considerably and the decrease in temperature difference will improve the uniformity of vaporization of the fog oil.

-It is to be understood that fog generating devices such as described above can be made as portable devices wherein the fog oil and fuel oil will be carried in tanks secured to the sleeve in which a compressed gas tank can be used as a pressure means for forcing the fuel from the tanks. Also, such devices can be used with fuel oil and fog oil under atmospheric pressure by gravity feed; however, these are not as efiicient an operation as those devices wherein the fuel and fog oil are pressurized.

Heretofore, valveless pulsejets have been used as post hole diggers in ice or frozen ground and for the purpose of melting ice from certain structures. FIG. 5 illustrates a valveless pulsejet which can be converted from an ice melting device to a fog generator or from a fog generator to an ice melting device. This device is made the same as described for FIG. 1 with exception that the fog-oil exhaust gas section as described for FIG. 1 is made as a detachable member such that the sleeve portion 41 is detachable at a position 42 slightly to the rear of the end 17 of the exhaust of the pulsejet. Also, the sleeve 11 is provided with a detachable cap 43 at the front end which is removable to permit air flow between the sleeve and the pulsejet when the device is used as a deicing device. The device is also provided with a swivel type mounting bracket 44 or provided with handles for portability by one or two men.

When the fog generating device is used for other purposes, the detachable mixing chamber 41 and the detachable cap 43 are removed as well as the fog oil feed lines to the ports 23. Removal of the detachable cap provides a two inch diameter opening for the entry of atmospheric cooling air. The operation of the pulsejet combustor engine is the same as described above and during operation the high velocity exhaust gas of the pulsejet aspirates cooling air flow around the engine and expels the heated air with the engine exhaust to form a high capacity hot gas output. The additional air flow from the front which is pulled over the engine increases the supply of hot fluid at the outlet to provide greater deicing capabilities. In use of the fog generator as a deicer, the atmospheric air is also aspirated through the fog oil inlet ports 23 as Well as from the front. The air inlet through the fog oil ports tends to cool the inlet tube 12 as the air flows thereby and also supplies additional air for cooling the engine. In use as a deicer, different shaped exhaust nozzles secured to the exhaust pipe can be used for deflecting the exhaust gases in different directions as desired.

Particles in the atmosphere scatter lights effectively with a definite relationship between the color of the transmitted light and the particle size. Since smoke generators must screen against light of varying wavelengths and it is not possible to produce fog with perfectly uniform particle size in a generator designed for field use, the desired range of particle size has been established as between 0.6 to 0.7 micron in diameter. Procedures for determining particle size have been fairly well established if the particles are reasonably uniform in size. If the sun is shining the color of the suns disc is observed from within the fog cloud and compared with the colors on a sun disc chart which gives the particle size of the corresponding color. The tabulation below illustrates the manner in which particle sizes and the condition of the fog are determined:

Particle Color of Sun Disc Condition of Size Fog (Micrcns Diameter) Deep orange Too dry 5 Light orange with a touch of pink Dry .6 Delicate pink with a touch of lavender Optimum..-" 64 Light blue (almost clear) Slightly wet .68

Blue Too wet 8 TABLE 1 Performance characteristics of a 3 /2 inch valveless pulsejet smoke or fog generator Range of particle size, diameters .6.7 micron Fuel-diesel oil Fuel pressure100 p.s.i.g. Fog oil-Type SGF-l, MIIr-F-1207OA Fog oil pressure-135 p.s.i.g.

AMBIENT TEMPERATURE80 F.

Fuel Rate (lb./hr.)- 29. 5 33. 5 36.0 42.0 43.0 44.0 45. 5 Fuel Rate (gaL/hr.) 4. 27 4.86 5. 23 6. 09 6. 23 6. 3S 6. 6 Fog Oil Rate (lb/hr.) 289. 8 345.0 292. 2 304. 8 360.0 Fog Oil Rate (gaL/hr.) 37. 7 244. 8 38. l 39. 46. 8 Fog Oil Temp.

(f F. .l 945 840 930 800 840 Fog Particle Size D (Microns) .6 68 6 64 68 1 Unable to generate fog at this fuel rate.

TABLE 2 Performance characteristics of a 3 /2 inch valveless pulsejet smoke or fog generator Range of particle size, diameters .6.'( micron Fuel-diesel oil Fuel pressure-100 p.s.i.".

Fog oil-Type sor a, inn-1207014 Fog oil pressure6 p.s.1.g.

AMBIENT TEMPERATURE-80 F.

Fuel Rate (lb./hr.) 30. 5 33. 5 34. 0 38.0 44.0 47. 5 50.0 Fuel Rate (gaL/hr.) 4. 42 4. 86 4. 93 5. 51 6. 38 6. 89 7. 25 Fog Oil Rate (lb/hr.) 325.2 204.8 360.0 384. 6 364. 8 360.0 240.0 Fog Oil Rate I (gal/hr.) 43.1 52.3 47.7 51.0 48.3 47.7 31.8 Fog Oil Temp.

Fog Particle Size -D (Microns)-.. .64 .6 .64 .64 .04

AMBIENT TEMPERATURE- F.

1 Unable to control particle size at this fuel rate (variable between .5-.8 micron).

2 Unable to generate fog at this fuel rate.

It has been determined that a change of only plus or minus 50 from the optimum temperature is sometimes sufficient to produce particle sizes outside the desired range, therefore considerable care must be taken in positioning the thermocouple within the mixture chamher. The location of the thermocouple must be such that the air flow pulled back into the mixing chamber by the return of the combustion products is not suflicient to have an effect on the thermocouple. In the device shown, the thermocouple is located 7 /2 inches from the exit and one inch from the axis of the exhaust tube.

In accordance to the present invention, valveless pulsejet smoke or fog generators capable of burning various type fuels and vaporizing various types of fog oils have been disclosed. Obviously, larger size pulsejet devices can be made and for greater output of fog, two or more pulsejets, as disclosed, can be parallel in pairs with the exhaust into a common duct where the fog will be ejected from the common duct. Such devices will produce much greater fogs than those of a single unit.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An apparatus for producing dispersions of atomized liquid particles comprising a resonant pulsejet engine having a combustion chamber and an exhaust tube extending linearly therewith, a sleeve of larger diameter than said pulsejet engine surrounding said engine and spaced therefrom, said sleeve extending beyond said exhaust to provide a gaseous mixing chamber, means for feeding a fluid of substance to be atomized over the outer surface of said jet engine within the spacing between said engine and said sleeve, means for supplying a fuel to the combustion chamber of said engine and means for supplying air to be mixed with said fuel to provide a fuel air mixture for said jet engine.

2. An apparatus for producing dispersions of atomized liquid particles comprising a resonant pulsejet engine having a combustion chamber and an exhaust tube extending linearly therewith, a sleeve of larger diameter than said pulsejet engine surrounding said engine and spaced therefrom, said sleeve extending beyond said exhaust tube to provide a gaseous mixing chamber, means for admitting a fluid substance to be atomized into the spacing between said combustion chamber, said exhaust tube and said sleeve surrounding said engine, means for supplying a fuel to the combustion chamber of said jet engine and means for supplying air to be mixed with said fuel to provide a fuel-air mixture for said jet engine,

3. An apparatus for producing dispersions of atomized liquid particles comprising a resonant valveless pulsejet engine having a combustion chamber and an exhaust tube extending linearly therewith, a sleeve of larger diameter than said pulsejet engine surrounding said engine and spaced therefrom, said sleeve extending beyond said exhaust tube to provide a gaseous mixing chamber, means for injecting a fog producing oil into the spacing between said combustion chamber and said sleeve surrounding said combustion chamber, means for injecting fuel into said combustion chamber and means for admitting air intosaid combustion chamber to provide a fuel-air mixture for said jet engine.

4. An apparatus for producing fog or smoke which comprises a resonant valveless pulsejet engine of general tubular form comprising a combustion chamber closed at the forward end and opening to the rearward into an exhaust section connected therewith, ignition means in the combustion chamber, a combustible fuel-air mixture inlet tube extending into said combustion chamber, a sleeve closed at the forward end and surrounding said valveless pulsejet engine, spaced therefrom and extending rearwardly beyond the rear end of said exhaust section to provide a gaseous mixing chamber, fog oil admittance port located in the forward end of said sleeve at the axis thereof and ports in the sleeve toward the rear end located on opposite sides of said fuel-air inlet tube, and means for admitting fuel into the forward end of said fuel-air inlet tube.

5. An apparatus for producing fog or smoke as claimed in claim 4 wherein said gaseous mixing chamber and a cap are detachable from said sleeve.

6. An apparatus for producing fog or smoke which comprises a resonant valveless pulsejet engine of general tubular form comprising a combustion chamber closed at the forward end and opening to the rearward into an exhaust section of smaller diameter connected therewith, the rear end of said exhaust section increasing in diameter equal to the diameter of said combustion chamber, a combustible fuel-air mixture inlet tube extending into said combustion chamber, ignition means in the combustion chamber, a sleeve closed at the forward end, surrounding said valveless pulsejet engine, spaced therefrom. and extending rearwardly beyond the rear end of said exhaust section to provide a gaseous mixing chamber, a fog fuel admittance port located in the forward end of said sleeve at the axis thereof, additional fog fuel ports located in the sleeve rearward of said fuel-air inlet and on opposite sides thereof, and means for admitting fuel into the forward end of said fuel-air inlet tube.

7. An apparatus for producing fog or smoke as claimed in claim 6 wherein said pulsejet engine is rigidly secured to said sleeve at said fuel-air inlet coaxial with said sleeve and by separation brackets slidably connected to the exhaust section to permit linear movement of said valveless jet engine within said sleeve due to expansion and contraction.

8. An apparatus for producing fog or smoke which comprises a resonant valveless pulsejet engine of general tubular form comprising a combustion chamber closed at the forward end and opening to the rearward into an exhaust section connected therewith, a combustible fuel-air mixture inlet tube extending into said combustion chamber, a sleeve surrounding said pulsejet engine closed at the forward end, spaced from said pulsejet engine and extending rearwardly beyond the rear end of said exhaust section to provide a gaseous mixing chamber, a fog oil admittance port located in the forward end of said sleeve at the axis thereof and ports in the sleeve toward the rear end located on opposite sides of said fuel-air inlet tube, a supply line for admitting fog oil into said ports, said supply line coiled about said sleeve in the vicinity of said pulsejet combustion chamber and also coiled in the vicinity of the opening to said air inlet tube prior to admitting fog oil to said ports, and means for admitting fuel into the forward end of said fuel-air inlet tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,857,332 Tenney et a1 Oct. 21, 1958 

1. AN APPARATUS FOR PRODUCING DISPERSIONS OF ATOMIZED LIQUID PARTICLES COMPRISING A RESONANT PULSEJET ENGINE HAVING A COMBUSTION CHAMBER AND AN EXHAUST TUBE EXTENDING LINEARYL THEREWITH, A SLEEVE OF LARGER DIAMETER THAN SAID PULSEJET ENGINE SURROUNDING SAID ENGINE AND SPACED THEREFROM, SAID SLEEVE EXTENDING BEYOND SAIDD EXHAUST TO PROVIDE A GASEOUS MIXING CHAMBER, MEANS FOR FEEDING A FLUID OF SUBSTANCE TO BE ATOMIZED OVER THE OUTER SURFACE OF SAID JET ENGINE WITHIN THE SPACING BETWEEN SAID ENGINE AND SAID SLEEVE, MEANS FOR SUPPLYING A FUEL TO THE COMBUSTION CHAMBER OF SAID ENGINE AND MEANS FOR SUPPLYING AIR TO BE MIXED WITH SAID FUEL TO PROVIDE A FUEL AIR MIXTURE FOR SAID JET ENGINE. 